This application relates to a method for preparing semiconductor materials and devices, and more particularly to a method of preparing defect free layers of semiconductor materials for use as a substrate or a buffer layer in a semiconductor device.
The growth of high quality, defect free semiconductor materials for use as a substrate or a buffer layer in a semiconductor device is a prerequisite for the subsequent growth of high quality semiconductor layers in the device.
The preparation of defect free semiconductor materials is easiest when a substrate of the same material is used. However, often times this is not possible and defects are created during the preparation of the semiconductor at the interface between the semiconductor and the substrate, as a result of the lattice and thermal mismatch between the semiconductor and the substrate materials. Buffer layers and other multi-layer schemes are often used to form a transition between the substrate and the semiconductor layer, but these have proven insufficient in many cases.
For example, in the case of III-Nitride semiconductor materials, many of the defects propagate nearly along the growth direction, that is perpendicular to the substrate/layer interface, without stopping as the film is grown thicker. It is therefore necessary to effectively stop the propagation of these defects.